1. Field of the Invention
The present invention relates to electromagnetic support systems, including systems for magnetically levitating, suspending, constraining, and/or isolating vibrating objects.
2. Discussion of the Related Art
Electromagnetic support systems have a wide variety of uses. They may be employed, for example, to support vibrating mechanical equipment in marine vessels and other apparatuses. U.S. Pat. No. 5,022,628, for example, describes a system of electromagnets and sensors for attenuating vibrations in a flexible machinery raft.
Electromagnetic support systems may also be used to constrain rotating shafts, to provide stable levitation for transportation systems, and to support precision measuring equipment, for example, and to attenuate acoustic vibrations that would otherwise be transmitted to connected structures. Other examples of electromagnetic support systems are provided in U.S. Pat. Nos. 5,387,851 (Nuscheler et al.), 5,291,967 (Aoki), 5,126,641 (Putman et al.), and 5,011,108 (Chen et al.).
In general, there is a need in the art for electromagnetic support systems that provide relatively high vibration attenuation performance. In addition, there is a need for electromagnetic support systems that have relatively low mechanical and signal processing requirements.
The disadvantages of the prior art are overcome to a great extent by the present invention.
The present invention relates to a support system that has at least one device for applying electromagnetic forces between first and second objects, and an elastomeric structure (such as a rubber pad) for supporting the electromagnetic device. In a preferred embodiment of the invention, the electromagnetic device is positively controlled as a function of (A) the position of the first object with respect to the second object and (B) the position of the electromagnetic device with respect to the second object.
According to one aspect of the invention, an elastomeric pad structure is provided for each electromagnet. In a preferred embodiment of the invention, there may be a large number of electromagnets. All of the electromagnets may be individually and dynamically controlled by the same controller.
According to another aspect of the invention, sensors are used to provide data to the controller. The sensors provide information representative of the relative positions and/or movements of the electromagnets.
The present invention also relates to the use of elastomeric connectors or other compliant devices (such as coil springs, pneumatic springs, or magnetic springs) to simplify the resonance patterns of vibrating objects. Simplifying the vibrational resonance patterns makes it easier to use signal processing to dynamically attenuate the remaining vibrations. The compliant devices may also be used to reduce the intensity of high frequency vibration transmission.
In a preferred embodiment of the invention, the compliant connector devices are formed of hard rubber. Such devices are economical, effective, easy to install, and durable.
According to another aspect of the invention, each compliant device resembles a lightly-damped but stiff spring. At high frequencies, the impedance mismatch between a massive magnet and a lightly-damped spring is greater than between a massive magnet and a heavily-damped spring. Consequently, high frequency vibration transmission is attenuated more effectively when the inherent damping associated with the compliant device is relatively low.
According to yet another aspect of the invention, the compliant devices are configured to permit rocking and/or rotational motion of the magnet relative to the hull. In particular, the devices are constructed such that rocking and/or rotational motions are not transmitted into the hull.
The present invention also relates to a method of supporting a vibrating object, such as a machiery raft, a rotating shaft, etc., with respect to a fixed object, such as a ship hull, an aircraft housing, or the floor of a factory.
An object of the invention is to provide compliant mounts for an electromagnetic support system. The compliant mounts, which may be formed of hard rubber, simplify the resonance pattern of the associated electromagnets, which makes it relatively easy to eliminate vibrations that would otherwise be transmitted to a connected structure. The present invention also may be used to simplify the dominant coupling and vibration transmission mechanism between the electromagnets and the connected structure (such as a hull).
Another object of the invention is to provide an electromagnetic support system that provides improved acoustic insulation. The invention may be used to reduce noise levels. It also may be used to prevent structural fatigue that might otherwise be caused by vibrations in the mechanical components of the system.
Another object of the invention is to provide an acoustic attenuation system with relatively uncomplicated signal processing requirements.
These and other features and advantages of the invention will become apparent from the following detailed description of preferred embodiments.